History of Life Part 3

Proterozoic Eon2.5 bya – 543 mya

stable continents first appear

Most life are Bacteria and Archaeans

first evidence of oxygen build-up in the atmosphere

This global catastrophe spelled doom for many bacterial groups &

made possible the explosion of eukaryotic forms.

EndosymbiosisWhat does it mean?

The rise of Eukarya 1.8 bya

Endo = withinsym = togetherbiosis = lifeEndosymbiosis = organisms of a different species living together, with one of the organisms living within the other

Symbiosis between different species of eubacteria&

between archeabacteria and eubacteria

Prokaryotes lead to Eukaryotes

Endosymbiosis Increases Organism Complexity

Croanoflagelado:-last unicellular ancestor of all eukaryotes-Characteristics similar to modern protista

800 mya: 1st-multicellular organism Sphaeroeca, a colony of choanoflagellates ~230 individuals cooperatively linked protists

850 MYA First Fungi

the fossil on right are fungal filaments resemble living filaments of common Candida species.

the fossil at right has preserved the perithecium with spores used for reproduction.

Amber fossils

760 MYA-First Animal

Otavia antiqua

-a sea sponge

Typical day in a late PreCambrian sea…

Trilobites: the 1st exoskeletons.

Finally the ocean is full of animals with hard parts… by the early Paleozoic there are lots of animals that can form fossils.

Cambrian Explosion:

~570mya- 500mya

Cambrian Explosion: A sudden explosion of complex, multicellular life at the beginning of the Paleozoic

Many of these early animals looked very strange, unlike any animals we find on Earth today.

Opibinia… 1st macroscopic predator

Most of the major phyla originated over several million years during the early Paleozoic…

520 mya Pikaia: 1st Chordate

Typical day in late PreCambrian sea…

Jawless Fish•Earliest Fish 500 mya

Armored Fish

Lobed Finned Fish

Plants Move Onto Land

480 MYA- First Land Plant

The cryptospores are the oldest land plant fossils found.

Petrified fossils

Animals Move Onto Land

Fish to Amphibian

Tiktaalik: fish-amphibian transition fossil

370 mya: Amphibians

~310 mya 1st REPTILES

first animals with backbones able to live on dry land

Ex Thecodont

Earliest DinosaurEoraptor

•230 mya

•Argentina

•3 ft long

•10 lbs

•Carnivor

•Bipedial

“dawn theif”

Flying ReptilesAppeared ~ 230mya, around the same time as dinosaurs.

They were the first vertebrates to fly.

Georgia

Eoraptor site

Reptiles to Mammals

Earliest MammalMegazostrodon

• found in Africa

•~ 220 mya

•4-5 inches long

•Carnivore

•Laid eggs

mega-large, zostros-girdle odon-tooth

Reptiles to Birds

Feathers ?…

most small theropod dinosaurs were covered in feathers.

Earliest BirdArchaeopteryx

“Ancient wing”

~150 mya

The late Cretaceous was a time of intense volcanic activity.

For many millions of years the atmosphere was modified by the release of volcanic gases and ash.

Major Extinction Event•65 mya

•65% all species become extinct, including all non-avian dinosaurs

•Worse for large animals

•Marked the end of the Mesozoic

Impact at Chixulub in Yuccatan Peninsula

Post Ice Age: Large Mammals

Ground Sloth: 20 mya

175,000 yr ago- Homo sapiens

1.8 MYA- Home erectus

first to travel long distances & use fire

2.5 MYA- Homo habilisFirst tool user

3.9 MYA- Australopithecus

afarensis

First bipedalism